The present invention relates to protective covers for a gas sensor, a gas sensor and a method of manufacturing a gas sensor. Hereinafter, the term “front” refers to a sensing end side with respect to the axial direction of a gas sensor, and the term “rear” refers to a side opposite to the front side.
Japanese Laid-Open Patent Publication No. 11-352095 discloses a conventional type of gas sensor as shown in FIG. 8, which comprises a cylindrical metallic housing 81, a sensor element 82, a heater 83, metallic protective covers 84 and 85, a ground terminal 91, an output terminal 92, a ground lead 93, an output lead 94, a pair of heater terminals 95 (only one shown) and heater leads (not shown). The housing 81 has a metallic shell 81a and an inner tube 81b fixed to each other, although it can alternatively be formed into one piece. The sensor element 82 is disposed axially in the housing 81 with a sensing portion thereof protruded from a front end of the housing 81, and the heater 83 is inserted in the sensor element 82. The ground and output terminals 91 and 92 are fitted to a rear end of the sensor element 82 to make electrical connection between the sensor element 82 and the ground and output leads 93 and 94, whereas the heater terminals 95 are fitted to a rear end of the heater 95 to make electrical connection between the heater 83 and the heater leads. The protective cover 84 is attached to a front end portion of the housing 81 to cover the sensing portion of the sensor element 82. The protective cover 85 is attached to a rear end portion of the housing 81 to cover the ground and output terminals 91 and 92 and the heater terminals 95 with the ground and output leads 93 and 94 and the heater leads projected rearwardly from the protective cover 85.